There is a procedure in the epic owners manual for seating the prop on the shaft. Since it is a tapered shaft, the prop can seat farther back if you make it fit the shaft better. You are supposed to check it with Prussian Blue, if there is less than 60% contact area, you should seat the prop. I don't have any Prussian blue in my back pocket, or a way to measure 60% contact, so I just went through the procedure anyway. It got rid of strange vibrations under load.
Pull off prop.
Put valve lapping compound on shaft (abrasive fluid you can get from an auto parts store)
Slide the prop onto the shaft, turn it 10 times clockwise, then 10 times CCW until you've done it 100 times.
You are supposed to check it again after that with the blue stuff.